Label-free mapping of microstructural organisation in self-aligning cellular collagen hydrogels using image correlation spectroscopy

Hydrogels have emerged as promising biomaterials for regenerative medicine. Despite major advances, tissue engineers have faced challenges in studying the complex dynamics of cellmediated hydrogel remodelling. Second harmonic generation (SHG) microscopy has been a pivotal tool for non-invasive visualization of collagen type I hydrogels. By taking into account the typical polarization SHG effect, we recently proposed an alternative image correlation spectroscopy (ICS) model to quantify characteristics of randomly oriented collagen fibrils. However, fibril alignment is an important feature in many tissues that needs to be monitored for effective assembly of anisotropic tissue constructs. Here we extended our previous approach to include the orientation distribution of fibrils in cellular hydrogels and show the power of this model in two biologically relevant applications. Using a collagen hydrogel contraction assay, we were able to capture cell-induced hydrogel modifications at the microscopic scale and link these to changes in overall gel dimensions over time. After 24 h, the collagen density was about 3 times higher than the initial density, which was of the same order as the decrease in hydrogel area. We also showed that the orientation parameters recovered from our automated ICS model match values obtained from manual measurements. Furthermore, regions axial to cellular processes aligned at least 1.5 times faster compared with adjacent zones. Being able to capture minor temporal and spatial changes in hydrogel density and collagen fibril orientation, we demonstrated the sensitivity of this extended ICS model to deconstruct a complex environment and support its potential for tissue engineering research

Engineered neural tissue with Schwann cell differentiated human dental pulp stem cells: potential for peripheral nerve repair?

Despite the spontaneous regenerative capacity of the peripheral nervous system, large gap peripheral nerve injuries (PNIs) require bridging strategies. The limitations and suboptimal results obtained with autografts or hollow nerve conduits in the clinic urge the need for alternative treatments. Recently, we have described promising neuroregenerative capacities of Schwann cells derived from differentiated human dental pulp stem cells (d-hDPSCs) in vitro. Here, we extended the in vitro assays to show the pro-angiogenic effects of d-hDPSCs, such as enhanced endothelial cell proliferation, migration and differentiation. In addition, for the first time we evaluated the performance of d-hDPSCs in an in vivo rat model of PNI. Eight weeks after transplantation of NeuraWrap™ conduits filled with engineered neural tissue (EngNT) containing aligned d-hDPSCs in 15-mm rat sciatic nerve defects, immunohistochemistry and ultrastructural analysis revealed ingrowing neurites, myelinated nerve fibres and blood vessels along the construct. Although further research is required to optimize the delivery of this EngNT, our findings suggest that d-hDPSCs are able to exert a positive effect in the regeneration of nerve tissue in vivo

Evaluatie en waardering van de archeologische sites Rooiveld-Papenvijvers(Oostkamp, provincie West-Vlaanderen)

Dit rapport beschrijft de resultaten van het waarderend onderzoek op de archeologische sites Rooiveld-Papenvijvers in Oostkamp (West-Vlaanderen). De oudste sporen van menselijke activiteit in dit gebied gaan terug tot het mesolithicum. De bewoning tijdens het neolithicum is goed gedocumenteerd. Naast de opgegraven nederzetting te Waardamme Vijvers, leverde het proefsleuvenonderzoek te Papenvijvers een finaal-neolithische site (3de millennium cal BC). Verder leverden de beperkte prospecties op verschillende plaatsen, waaronder Oostkamp Nieuwenhove en Hertsberge Papevijvers, lithische artefacten op die naar alle waarschijnlijkheid tot een niet nader te bepalen fase van het neolithicum behoren. Deze situatie is vrij uniek voor Vlaanderen. Neolithische bewoning in de zandige delen van Vlaanderen ontbrak tot nog toe vrijwel, met uitzondering van enkele graven van de Klokbekercultuur. De opgraving te Waardamme Vijvers is bijzonder vanwege de ontdekking van de eerste en vooralsnog enige huisplattegrond uit het neolithicum in Vlaanderen. Sporen uit de bronstijd zijn dankzij de luchtfotografie heel talrijk in het gebied. Het desktop onderzoek leverde in totaal een negental cirkelvormige structuren op die naar alle waarschijnlijkheid mogen geïnterpreteerd worden als resten van grafheuvels uit de vroege en midden-bronstijd. Het is ook duidelijk dat de regio in de bronstijd bewoond was, o.a. door de opgraving op de site Waardamme Vijvers. Voor de ijzertijd is de situatie vermoedelijk gelijklopend. De enige nederzetting die uit deze periode werd aangetroffen komt eveneens uit de opgraving in Waardamme Vijvers. Voor de Romeinse periode beschikken we slechts over de sporen van een grafveld op Waardamme Vijvers en keramiekvondsten. Latere periodes zijn alleen via cartografische bronnen gedocumenteerd. Het rapport eindigt met aanbevelingen voor verder onderzoek en beheer van dit gebied

A new method to position and functionalize metal-organic framework crystals

With controlled nanometre-sized pores and surface areas of thousands of square metres per gram, metal-organic frameworks (MOFs) may have an integral role in future catalysis, filtration and sensing applications. In general, for MOF-based device fabrication, well-organized or patterned MOF growth is required, and thus conventional synthetic routes are not suitable. Moreover, to expand their applicability, the introduction of additional functionality into MOFs is desirable. Here, we explore the use of nanostructured poly-hydrate zinc phosphate (α-hopeite) microparticles as nucleation seeds for MOFs that simultaneously address all these issues. Affording spatial control of nucleation and significantly accelerating MOF growth, these α-hopeite microparticles are found to act as nucleation agents both in solution and on solid surfaces. In addition, the introduction of functional nanoparticles (metallic, semiconducting, polymeric) into these nucleating seeds translates directly to the fabrication of functional MOFs suitable for molecular size-selective applications

Nonlinear superchiral meta-surfaces: tuning chirality and disentangling non-reciprocity at the nanoscale.

Circularly polarized light is incident on a nanostructured chiral meta-surface. In the nanostructured unit cells whose chirality matches that of light, superchiral light is forming and strong optical second harmonic generation can be observed

Aqueous Flow Reactor and Vapour-Assisted Synthesis of Aluminium Dicarboxylate Metal-Organic Frameworks with Tuneable Water Sorption Properties

Energy-efficient indoors temperature and humidity control can be realised by using the reversible adsorption and desorption of water in porous materials. Stable microporous aluminium-based metal-organic frameworks (MOFs) present promising water sorption properties for this goal. The development of synthesis routes that make use of available and affordable building blocks and avoid the use of organic solvents is crucial to advance this field. In this work, two scalable synthesis routes under mild reaction conditions were developed for aluminium-based MOFs: (1) in aqueous solutions using a continuous-flow reactor and (2) through the vapour-assisted conversion of solid precursors. Fumaric acid, its methylated analogue mesaconic acid, as well as mixtures of the two were used as linkers to obtain polymorph materials with tuneable water sorption properties. The synthesis conditions determine the crystal structure and either the MIL-53 or MIL-68 type structure with square-grid or kagome-grid topology, respectively, is formed. Fine-tuning resulted in new MOF materials thus far inaccessible through conventional synthesis routes. Furthermore, by varying the linker ratio, the water sorption properties can be continuously adjusted while retaining the sigmoidal isotherm shape advantageous for heat transformation and room climatisation applications

Integrated cleanroom process for the vapor-phase deposition of large-area zeolitic imidazolate framework thin films

Robust and scalable thin-film deposition methods are key to realize the potential of metal-organic frameworks (MOFs) in electronic devices. Here, we report the first integration of the chemical vapor deposition (CVD) of MOF coatings in a custom reactor within a cleanroom setting. As a test case, the MOF-CVD conditions for the zeolitic imidazolate framework-8 are optimized to enable smooth, pinhole-free, and uniform thin films on full 200 mm wafers under mild conditions. The single-chamber MOF-CVD process and the impact of the deposition parameters are elucidated via a combination of in situ monitoring and ex situ characterization. The resulting process guidelines will pave the way for new MOF-CVD formulations and a plethora of MOF-based devices

The origin of second harmonic generation hotspots in chiral optical metamaterials [Invited]

Novel ways to detect the handedness in chiral optical metamaterials by means of the second harmonic generation (SHG) process have recently been proposed. However, the precise origin of the SHG emission has yet to be unambiguously established. In this paper, we present computational simulations of both the electric currents and the electromagnetic fields in chiral planar metamaterials, at the fundamental frequency (FF), and discuss the implications of our results on the characteristics of experimentally measured SHG. In particular, we show that the results of our numerical simulations are in good agreement with the experimental mapping of SHG sources. Thus, the SHG in these metamaterials can be attributed to a strong local enhancement of the electromagnetic fields at the FF, which depends on the particular structure of the patterned metamaterial

Chemical diversity in a metal-organic framework revealed by fluorescence lifetime imaging

The presence and variation of chemical functionality and defects in crystalline materials, such as metal–organic frameworks (MOFs), have tremendous impact on their properties. Finding a means of identifying and characterizing this chemical diversity is an important ongoing challenge. This task is complicated by the characteristic problem of bulk measurements only giving a statistical average over an entire sample, leaving uncharacterized any diversity that might exist between crystallites or even within individual crystals. Here we show that by using fluorescence imaging and lifetime analysis, both the spatial arrangement of functionalities and the level of defects within a multivariable MOF crystal can be determined for the bulk as well as for the individual constituent crystals. We apply these methods to UiO-67, to study the incorporation of functional groups and their consequences on the structural features. We believe that the potential of the techniques presented here in uncovering chemical diversity in what is generally assumed to be homogeneous systems can provide a new level of understanding of materials properties